A luminaire (light fixture) is a device comprising at least one lamp for emitting illumination, and any associated socket, support and/or housing. A luminaire may take any of a variety of forms, such as a conventional ceiling or wall mounted luminaire, free standing luminaire or wall washer, or a less conventional form such as an illumination source built into a surface or an item of furniture, or any other type of lighting device for emitting illumination into an environment. The lamp refers to an individual light-emitting component within a luminaire, of which there may be one or more per luminaire. The lamp may also take any of a number of forms, such as an LED-based lamp, a gas-discharge lamp, or a filament bulb. An increasingly popular form of lamp is a retrofittable LED-based lamp comprising one or more LEDs as the means by which to emit illumination, but being made retrofittable into a luminaire designed for a traditional filament bulb or fluorescent tube.
A luminaire or even an individual lamp may also be equipped with a wireless communication interface allowing the luminaire or lamp to be controlled remotely by lighting control commands received from a user device such as a smartphone, tablet, laptop or desktop computer, or wireless wall-switch; and/or based on sensor readings received from one or more remote sensors. Nowadays, the communication interface can be included directly within the lamp itself (e.g. in the end-cap of a retrofittable replacement for a filament bulb or fluorescent tube). For example this can allow a user, through the user device, to turn the lamp's illumination on and off, to dim the illumination level up or down, to change the colour of the emitted illumination, and/or to create a dynamic (time varying) lighting effect. In one form, the communication interface is configured to receive the lighting control commands and/or to share sensor data via a local, short-range radio access technology such as Wi-Fi, 802.15.4, ZigBee or Bluetooth. Such lamps may sometimes be referred to as “connected” lamps.
One type of connected lamp is an instant-fit “tube LED” (TLED) lamp which retrofits into a luminaire designed for traditional fluorescent tubes. According to the instant-fit TLED approach, the existing fixed-output fluorescent ballast, the TLED lamp-holders and also all the electrical wiring within the luminaire remain unchanged. Via straightforward re-lamping, existing “dumb” fluorescent tubes (or even “dumb” TLED tubes) can be exchanged with dimmable connected TLEDs each having an individual, integrated wireless radio.
In other “smart” or “connected” lighting applications, there is provided the ability to embed data into the illumination emitted by a luminaire, by modulating a property such as the intensity of the emitted light in order to encode the data (preferably at a high enough frequency to be beyond human perception or at least tolerable to humans). This is sometimes referred to as “coded light” (CL) or “visible light communication” (VLC).
For instance, each luminaire may be arranged to emit a different respective ID code unique to the respective luminaire (at least being unique within the system in question, e.g. within a given building). A look up table may also be made available to a mobile user terminal, e.g. being hosted on a server and made available via a local wireless network and/or the Internet, or being stored locally on the user terminal. The look up table maps at least one respective piece of information to each of the IDs, e.g. the location of the respective luminaire. By using a light sensor (e.g. camera) built into the user terminal, an application running on the user terminal can detect the ID embedded in the light currently encountered at the user's present location (e.g. the user points the camera up towards a particular luminaire). The application then accesses the look-up table to look-up the information mapped to the ID. E.g. if this information comprises the location of the respective luminaire, this can be taken as the approximate location of the user terminal (and therefore the user). In more sophisticated variants, the light and respective embedded IDs from a plurality of nearby luminaires can be used by the application to compute a more precise position fix, using measurements of the received coded-light signals (e.g. received signal strength, time-of-flight, and/or angle of arrival) and a suitable positioning algorithm (e.g. triangulation, trilateration, multilateration and/or fingerprinting).
Such techniques have a particular application for indoor positioning where satellite-based positioning systems (e.g. GPS, Galileo or GLONASS) cannot penetrate. However there is nothing to stop such positioning techniques being used outdoors as well. Either way, these positioning (i.e. localization) techniques can be used for a number of purposes such as navigation, i.e. displaying the user's current position to the user on a map on the user's terminal to help him/her find his/her way about; or providing location-dependent services, e.g. the user is only permitted to perform a certain action such as controlling the lighting or heating heating or making a location dependent payment on condition of being detected to be within a certain predefined zone.
Or in yet further applications, other information may be mapped to the IDs such as location-based infotainment or advertising. Or as yet another possibility, information of interest could be embedded directly (explicitly) into the light rather than requiring a look-up.